Apparatus for withdrawing air from suction boxes



Oct. 16, 1928. 1,688,216

M. WENZEL APPARATUS FOR WITHDRAWING AIR FROM SUCTION BOXES Filed July 7, 1928 Patented Oct. 16, 1928.

UNITED STATES 1,688,216- PATENT OFFICE.

MAX WENZEL; OF MULDENSTEIN, NEAR BITTERFELI), GERMANY.

APPARATUS FOR WITHDR-AXVING AIR FROM SUCTION BOXES.

Application filed July 7, 1928, Serial No, 290.933, and in Germany October 29, 1826,

This invention relates to apparatus for withdrawing air from suction boxes, and with regard to certain more specific features to said apparatus to be used in connection with suction boxes for paper machines and the like.

Among the several objects of the invention may be noted the provision of av more eco nominal and less cumbersome means foref- Hl footing an abstraction of air or the like from a. series of suction chambers adapted to be operated at diiierent pressures. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of'elelnents, steps and sequence of steps, features of construction, and arrangements of parts which will be exemplified in the structure hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which is illustrated one of various possible embodiments of the invention, the single figure illustrates the improved apparatus. 1

The general type of paper machine suction boxes to which this invention applies are known in the art, and an example of such a suction box is disclosed in my United States Patent 1,518,116, issued December 2, 1924. Another example is disclosed in my German Patent 401,935, issued September 15, 1924. It is to be understood that the invention applies to boxes wherein a plurality of rolls are served by one box, as shown in said patents, and a new and improved type wherein each roll is served by one box, as disclosed in my copending United States patent application entitled Roll suction device, filed of even date (file 3121). The invention can also be used on flat and other types of suction boxes.

It is customary to operate these suction boxes of paper machines (for eliminating water from cellulose and the like at partial vacuums of various degrees. This is usually done by increasing the partial vacuum from suction box to suction box in accordance with the progressive elimination of Water from the web of paper passing over successive boxes on roll-supported conveyor wire or the like. Up until the present time these various degrees of negative pressure in the suction boxes were induced by causing an air pump to produce a partial vacuum required, for instance in the last suction box, while the negative Someto as multi-stage vacuum pumps. The various degrees of vacuum of this class of centrifugal pump are adapted in regard to their number, the value of the negative pressure and the air efficiency, to the negative pressures and volumes of air required at the various suction devices or groups of suction devices, and each one of the various stages of the blower or pump is provided with a. suction pipe. By a tubular connection between each suction pipe of the various stages of the blower and the corresponding suction boxes or groups of suction boxes, the combinations for the operation in accordance with the new method areprovided.

The figure shows an embodiment of a plant illustrating in side elevation a movable longitudinal sieve or netting 1 which moves preferably in the direction shown by vector 3. Letters a a a a, indicate the suction boxes, letters 6 b b b the communicating conduits leading to the blower or suction device, where said conduits connect to the suction pipes of the various stages of the blower (Z, as indicated at d d d (Z Letter d indicates the final stage of the blower having the exhaust 5 Letter 0 represents the driving motor of the blower d and c c c 0 indicate the water discharge pipes of the suction boxes for draining ofi' water sucked out of the paper passing over the boxes on the netting 1.

The operation is as follows:

The negative or subatmospheric pressures of the various blower stages, chambers or steps connected with suction pipes d d d,, 05 are slightly higher than the maximum negative pressure required in the corresponding suction boxes a a a a in order to compensate for the losses of pressure in the communicating conduits.

The pump then extracts the air from the suction boxes. The extracted water flows into the pipes c c c and to a sump 5. The chamber, stage or step (1 of the blower draws the highestnegative pressure, because, among other things, it has the lowest back pressure, the other stages sucking air therefrom in series. Stage al sucks air from box a and exhausts to staged Stage (i draws air from box a and from stage 01 and exhausts to stage (1 and so on, until stage (15,, which takes the exhaust of stage (1,, itself exhaust-s into the atmosphere. The stage (Z therefore, is connected with the last suction box a, requiring the best vacuum. As stated, the stage (i receives the air drawn in bysuction by the stage 03,, compresses this air to the next negative pressure and withdraws air corresponding to this negative pressure from the suction box 11,. The other stages operate accordingly. the last stage d exhausting this air from the various blower chambers or steps d (Z (i d,, at atmospheric pressure, so that this air may be discharged into the atmosphere through the conduit (6 Clearly a plurality of suction boxes may be connected with any step or chamber of the blower. A variation of the output as to volume and as to pressure is made feasible by varying the number of revolutions of the blower or by throttling respectively the ultimate discharge pipe 6 as by a valve 7 or by throttling the suction conduits of the various steps or chambers as by valves 9, 10, 11, 12. In general, however, this lastnamed variation is required within relatively narrow limits only, inasmuch as the basic variations of the various partial vacuums are furnished by the multi-stage action of the blower itself, which steps are adapted to the operation of the paper machine to which the device is connected.

' It is to be understood that the present invention is not limited to multi-stage centrifugal suction apparatus but may employ any multi-stage'class of pump, such as a. multistage reciprocating pump or others. The multi-stage action permits one pump to be used for Various degrees of suction, without excessive throttling and eliminates the use of an excessive number of suction machines each operating to compress to atmospheric pressure.

. For instance, it will be seen that in my apparatus stage 11,, which draws the best vacuum needs only compress up to the sub-atmospheric' pressure of stage cl into which it exhausts and so on, the last stage d which must pump to atmosphere sucking a more moderate vacuum.

This invention, among other things, effects what is known as a bleeding action from each of various chambers to be evacuated to each of various stages'of compression in a multistage evacuating pump.

It will be seen that all the vacuums may be varied at once by varying the revolutions of the single pump d and this is also a feature intended to be covered hereby.

In view of the above. it will be seen that the several objects of the invention are achieved and other ad vautageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter conained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. Suction apparatus for paper machines comprising in combination, suction boxes, a multistage vacuum pump and means communicating between separate stages of the pump and separate suction boxes.

2. Suction apparatus for paper machines comprising in combination, suctionboxes, a

multi-stage centrifugal vacuum pump and means communicatlng between separate stages of the pump and separate suction boxes.

3. Suction apparatus for paper machines comprising in combination, suction boxes, a multi-stage vacuum pump, means communicating between separate stages ofthe pump and separate suction boxes, a discharge for said pump for effecting discharge from several stages and means for throttling said discharge whereby subatmospheric pressures within said boxes may be varied.

4. Suction apparatus for paper machines comprising in combination, suction boxes, a multi-stage vacuum pump, means communicating between separate stages of the pump and separate suction boxes, said pump being adapted to have its rate of action varied.

5. Suction apparatus for paper machines comprising in combination, suction boxes, a multi-stage centrifugal vacuum pump, means communicating between separate stages of the pump and separate suction boxes,'said pump being adapted to have its rate of rotation varied.

In testimony whereof, I have signed my name to this specification this 8th day of June, 1928.

MAX WENZEL. 

